Glyceraldehyde-3-phosphate dehydrogenase present in extracellular vesicles from Leishmania major suppresses host TNF-alpha expression

The protein cargo of extracellular vesicles correlates with the epigenetic aging clock of exercise sensitive DNAmFitAge

Extracellular vesicles (EVs) are implicated in inter-organ communication, which becomes particularly relevant during aging and exercise. DNA methylation-based aging clocks reflect lifestyle and environmental factors, while regular exercise is known to induce adaptive responses, including epigenetic adaptations. Twenty individuals with High-fitness (aged 57.7 ± 9.8 years) and twenty Medium-Low-fitness (aged 57.5 ± 9.7 years) subjects provided blood samples. EVs were isolated from the samples using a size exclusion chromatography (SEC)-based method, and their protein content was analyzed by mass spectrometry (MS). Acceleration of the biological age estimator DNAmFitAge (AgeAccelFit) was associated with the protein cargo of EVs, whereas PhenoAge and GrimAge acceleration did not show a significant relationship. This finding suggests that the epigenetic aging-modulating role of exercise may involve inter-organ communication via EVs. Set Enrichment Analysis was performed to identify enriched Gene Ontology (GO) terms for sets of proteins that were either correlated with AgeAccelFit or detected exclusively in individuals with high levels of aerobic fitness. The protein cargo of EVs further suggests that inter-organ communication influences inflammation, the immune system, cellular repair, adhesion, metabolism and coagulation. Our findings help to understand the preventive role of exercise, which could be mediated in part by EVs.

The biology and function of extracellular vesicles in immune response and immunity

Extracellular vesicles (EVs), such as ectosomes and exosomes, contain DNA, RNA, proteins and are encased in a phospholipid bilayer. EVs provide intralumenal cargo for delivery into the cytoplasm of recipient cells with an impact on the function of immune cells, in part because their biogenesis can also intersect with antigen processing and presentation. Motile EVs from activated immune cells may increase the frequency of immune synapses on recipient cells in a proximity-independent manner for local and long-distance modulation of systemic immunity in inflammation, autoimmunity, organ fibrosis, cancer, and infections. Natural and engineered EVs exhibit the ability to impact innate and adaptive immunity and are entering clinical trials. EVs are likely a component of an optimally functioning immune system, with the potential to serve as immunotherapeutics. Considering the evolving evidence, it is possible that EVs could be the original primordial organic units that preceded the creation of the first cell.

Anchorless Bacterial Moonlighting Metabolic Enzymes Modulate the Immune System and Contribute to Pathogenesis

Moonlighting proteins (MPs), characterized by their ability to perform multiple physiologically unrelated functions without alterations to their primary structures, represent a fascinating class of biomolecules with significant implications for host-pathogen interactions. This Review highlights the emerging importance of metabolic moonlighting proteins (MetMPs) in bacterial pathogenesis, focusing on their non-canonical secretion and unconventional surface anchoring mechanisms. Despite lacking typical signal peptides and anchoring motifs, MetMPs such as acetaldehyde alcohol dehydrogenase (AdhE) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) are secreted and localized to the bacterial surface under stress conditions, facilitating host colonization and immune evasion. The secretion of MetMPs, often observed during conditions such as resource scarcity or infection, suggests a complex regulation akin to the overexpression of heat shock proteins in response to environmental stresses. This Review proposes two potential pathways for MetMP secretion: membrane damage-induced permeability and co-transportation with traditionally secreted proteins, highlighting a remarkable bacterial adaptability. Biophysically, surface anchoring of MetMPs is driven by electrostatic interactions, bypassing the need for conventional anchoring sequences. This mechanism is exemplified by the interaction between the bifunctional enzyme AdhE (known as Listeria adhesion protein, LAP) and the internalin B (InlB) in Listeria monocytogenes, which is mediated by charged residues facilitating adhesion to host tissues. Furthermore, MetMPs play critical roles in iron homeostasis, immune modulation, and evasion, underscoring their multifaceted roles in bacterial pathogenicity. The intricate dynamics of MetMP secretion and anchoring underline the need for further research to unravel the molecular mechanisms underpinning these processes, offering potential new targets for therapeutic intervention against bacterial infections.

High-throughput surface epitope immunoaffinity isolation of extracellular vesicles and downstream analysis

Extracellular vesicles (EVs), including exosomes, have significant potential for diagnostic and therapeutic applications. The lack of standardized methods for efficient and high-throughput isolation and analysis of EVs, however, has limited their widespread use in clinical practice. Surface epitope immunoaffinity (SEI) isolation utilizes affinity ligands, including antibodies, aptamers, or lectins, that target specific surface proteins present on EVs. Paramagnetic bead-SEI isolation represents a fit-for-purpose solution for the reproducible, high-throughput isolation of EVs from biofluids and downstream analysis of RNA, protein, and lipid biomarkers that is compatible with clinical laboratory workflows. This study evaluates a new SEI isolation method for enriching subpopulations of EVs. EVs were isolated from human plasma using a bead-based SEI method designed for on-bead and downstream analysis of EV-associated RNA and protein biomarkers. Western blot analysis confirmed the presence of EV markers in the captured nanoparticles. Mass spectrometry analysis of the SEI lysate identified over 1500 proteins, with the top 100 including known EV-associated proteins. microRNA (miRNA) sequencing followed by RT-qPCR analysis identified EV-associated miRNA transcripts. Using SEI, EVs were isolated using automated high-throughput particle moving instruments, demonstrating equal or higher protein and miRNA yield and recovery compared to manual processing. SEI is a rapid, efficient, and high-throughput method for isolating enriched populations of EVs; effectively reducing contamination and enabling the isolation of a specific subpopulation of EVs. In this study, high-throughput EV isolation and RNA extraction have been successfully implemented. This technology holds great promise for advancing the field of EV research and facilitating their application for biomarker discovery and clinical research.

Extracellular vesicles in parasitic diseases - from pathogenesis to future diagnostic tools

Parasitic diseases are still a major public health problem especially among individuals of low socioeconomic status in underdeveloped countries. In recent years it has been demonstrated that parasites can release extracellular vesicles that participate in the host-parasite communication, immune evasion, and in governing processes associated with host infection. Extracellular vesicles are membrane-bound structures released into the extracellular space that can carry several types of biomolecules, including proteins, lipids, nucleic acids, and metabolites, which directly impact the target cells. Extracellular vesicles have attracted wide attention due to their relevance in host-parasite communication and for their potential value in applications such as in the diagnostic biomarker discovery. This review of the literature aimed to join the current knowledge on the role of extracellular vesicles in host-parasite interaction and summarize its molecular content, providing information for the acquisition of new tools that can be used in the diagnosis of parasitic diseases. These findings shed light to the potential of extracellular vesicle cargo derived from protozoan parasites as novel diagnostic tools.

Global Remodeling of Host Proteome in Response to Leishmania Infection

The protozoan parasite Leishmania possesses an intrinsic ability to modulate a multitude of pathways in the host, toward aiding its own proliferation. In response, the host reprograms its cellular, immunological, and metabolic machinery to evade the parasite's lethal impact. Besides inducing various antioxidant signaling pathways to counter the elevated stress response proteins like heme oxygenase-1 (HO-1), Leishmania also attempts to delay host cell apoptosis by promoting anti-apoptotic proteins like Bcl-2. The downstream modulation of apoptotic proteins is regulated by effector pathways, including the PI3K/Akt survival pathway, the mitogen-activated protein kinases (MAPKs) signaling pathway, and STAT phosphorylation. In addition, Leishmania assists in its infection in a time-dependent manner by modulating the level of various proteins of autophagic machinery. Immune effector cells, such as mast cells and neutrophils, entrap and kill the pathogen by secreting various granular proteins. In contrast, the host macrophages exert their leishmanicidal effect by secreting various cytokines, such as IL-2, IL-12, etc. An interplay of various signaling pathways occurs in an organized network that is highly specific to both pathogen and host species. This Review analyzes the modulation of expression of proteins, including the cytokines, providing a realistic approach toward understanding the pathophysiology of disease and predicting some prominent markers for disease intervention and vaccine support strategies.

Importance of aspartate 4 in the Mg2+ dependent regulation of Leishmania major PAS domain-containing phosphoglycerate kinase

Magnesium is an important divalent cation for the regulation of catalytic activity. Recently, we have described that the Mg2+ binding through the PAS domain inhibits the phosphoglycerate kinase (PGK) activity in PAS domain-containing PGK from Leishmania major (LmPAS-PGK) at neutral pH 7.5, but PGK activity is derepressed at acidic pH 5.5. The acidic residue within the PAS domain of LmPAS-PGK is expected to bind the cofactor Mg2+ ion at neutral pH, but which specific acidic residue(s) is/are responsible for the Mg2+ binding is still unknown. To identify the residues, we exploited mutational studies of all acidic (twelve Asp/Glu) residues in the PAS domain for plausible Mg2+ binding. Mg2+ ion-dependent repression at pH 7.5 is withdrawn by substitution of Asp-4 with Ala, whereas other acidic residue mutants (D16A, D22A, D24A, D29A, D43A, D44A, D60A, D63A, D77A, D87A, and E107A) showed similar features compared to the wild-type protein. Fluorescence spectroscopic studies and isothermal titration calorimetry analysis showed that the Asp-4 is crucial for Mg2+ binding in the absence of both PGK's substrates. These results suggest that Asp-4 residue in the regulatory (PAS) domain of wild type enzymes is required for Mg2+ dependent repressed state of the catalytic PGK domain at neutral pH.

Guidelines for the purification and characterization of extracellular vesicles of parasites

Parasites are responsible for the most neglected tropical diseases, affecting over a billion people worldwide (WHO, 2015) and accounting for billions of cases a year and responsible for several millions of deaths. Research on extracellular vesicles (EVs) has increased in recent years and demonstrated that EVs shed by pathogenic parasites interact with host cells playing an important role in the parasite's survival, such as facilitation of infection, immunomodulation, parasite adaptation to the host environment and the transfer of drug resistance factors. Thus, EVs released by parasites mediate parasite-parasite and parasite-host intercellular communication. In addition, they are being explored as biomarkers of asymptomatic infections and disease prognosis after drug treatment. However, most current protocols used for the isolation, size determination, quantification and characterization of molecular cargo of EVs lack greater rigor, standardization, and adequate quality controls to certify the enrichment or purity of the ensuing bioproducts. We are now initiating major guidelines based on the evolution of collective knowledge in recent years. The main points covered in this position paper are methods for the isolation and molecular characterization of EVs obtained from parasite-infected cell cultures, experimental animals, and patients. The guideline also includes a discussion of suggested protocols and functional assays in host cells.

Extracellular Vesicles and Their Impact on the Biology of Protozoan Parasites

Extracellular vesicles (EVs) are lipid-membrane-bound structures produced naturally by all cells and have a variety of functions. EVs act as vehicles for transporting important molecular signals from one cell to another. Several parasites have been shown to secrete EVs, and their biological functions have been extensively studied. EVs have been shown to facilitate communication with the host cells (such as modulation of the host's immune system or promoting attachment and invasion into the host cells) or for communication between parasitic cells (e.g., transferring drug-resistance genes or factors modulating stage conversion). It is clear that EVs play an important role in host-parasite interactions. In this review, we summarized the latest research on the EVs secreted by protozoan parasites and their role in host-parasite and parasite-parasite communications.

Proteomic analysis of extracellular vesicles from tick hemolymph and uptake of extracellular vesicles by salivary glands and ovary cells

BACKGROUND

Extracellular vesicles (EVs) are a heterogeneous group of cell-derived membranous structures that are important mediators of intercellular communication. Arthropods transport nutrients, signaling molecules, waste and immune factors to all areas of the body via the hemolymph. Little is known about tick hemolymph EVs.

METHODS

Hemolymph was collected from partially fed Rhipicephalus haemaphysaloides and Hyalomma asiaticum ticks by making an incision with a sterile scalpel in the middle (between the femur and metatarsus) of the first pair of legs, which is known as leg amputation. EVs were isolated from hemolymph by differential centrifugation and characterized by transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA). Proteins extracted from the hemolymph EVs were analyzed by 4D label-free proteomics. The EVs were also examined by western blot and immuno-electron microscopy analysis. Intracellular incorporation of PHK26-labeled EVs was tested by adding labeled EVs to tick salivary glands and ovaries, followed by fluorescence microscopy.

RESULTS

In this study, 149 and 273 proteins were identified by 4D label-free proteomics in R. haemaphysaloides and H. asiaticum hemolymph EVs, respectively. TEM and NTA revealed that the sizes of the hemolymph EVs from R. haemaphysaloides and H. asiaticum were 133 and 138 nm, respectively. Kyoto Encyclopedia of Genes and Genomes and Gene Ontology enrichment analyses of identified proteins revealed pathways related to binding, catalytic and transporter activity, translation, transport and catabolism, signal transduction and cellular community. The key EV marker proteins RhCD9, RhTSG101, Rh14-3-3 and RhGAPDH were identified using proteomics and western blot. The presence of RhFerritin-2 in tick hemolymph EVs was confirmed by western blot and immuno-electron microscopy. We demonstrated that PKH26-labeled hemolymph EVs are internalized by tick salivary glands and ovary cells in vitro.

CONCLUSIONS

The results suggest that tick EVs are secreted into, and circulated by, the hemolymph. EVs may play roles in the regulation of tick development, metabolism and reproduction.

Francisella tularensis Glyceraldehyde-3-Phosphate Dehydrogenase Is Relocalized during Intracellular Infection and Reveals Effect on Cytokine Gene Expression and Signaling

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is known for its multifunctionality in several pathogenic bacteria. Our previously reported data suggest that the GAPDH homologue of Francisella tularensis, GapA, might also be involved in other processes beyond metabolism. In the present study, we explored GapA's potential implication in pathogenic processes at the host cell level. Using immunoelectron microscopy, we demonstrated the localization of this bacterial protein inside infected macrophages and its peripheral distribution in bacterial cells increasing with infection time. A quantitative proteomic approach based on stable isotope labeling of amino acids in cell culture (SILAC) combined with pull-down assay enabled the identification of several of GapA's potential interacting partners within the host cell proteome. Two of these partners were further confirmed by alternative methods. We also investigated the impact of gapA deletion on the transcription of selected cytokine genes and the activation of the main signaling pathways. Our results show that ∆gapA-induced transcription of genes encoding several cytokines whose expressions were not affected in cells infected with a fully virulent wild-type strain. That might be caused, at least in part, by the detected differences in ERK/MAPK signaling activation. The experimental observations together demonstrate that the F. tularensis GAPDH homologue is directly implicated in multiple host cellular processes and, thereby, that it participates in several molecular mechanisms of pathogenesis.

Holanamine, a Steroidal Alkaloid from the Bark of Holarrhena pubescens Wall. ex G. Don Inhibits the Growth of Leishmania donovani by Targeting DNA Topoisomerase 1B

Leishmaniasis is a group of neglected tropical diseases (NTDs) caused by about 20 species of obligate intracellular protozoan parasites of the genus Leishmania, which occurs in cutaneous, mucocutaneous, and visceral forms. Many researchers have sought to utilize natural products for novel and effective treatments to combat many infectious diseases, including leishmaniasis. Holarrhena pubescens Wall. ex G. Don (Apocynaceae) bark is a rich source of bioactive steroidal alkaloids. The total alkaloidal extract (IC₅₀ 6.12 ± 0.117 μg/mL), and the isolated alkaloid, holanamine, showed significant antileishmanial activity (IC₅₀ 2.66 ± 0.112 μM against AG83 and 3.80 ± 0.126 μM against BHU-575) against the Leishmania donovani parasite, better than miltefosine (IC₅₀ 19.61 ± 0.093 μM against AG83 and 23.20 ± 0.094 μM against BHU-575). Holanamine inhibited the L. donovani topoisomerase 1B (LdToP1B) in a non-competitive manner (IC₅₀ 2.81 ± 0.105 μM), indicating that it interacts with the free enzyme and enzyme-DNA complex without inhibiting human topoisomerase. Hydrogen bonding and hydrophobic interactions of holanamine with the N-terminal and hinge region of the large subunit of LTop1B is responsible for its potent antileishmanial activity, as shown by docking studies. Treatment with holanamine causes apoptotic-like cell death by generating cellular and mitochondrial reactive oxygen species, disrupting the mitochondrial membrane potential and inducing ultrastructural alterations in the promastigotes. Holanamine effectively clears intracellular amastigotes but minimally affects host macrophages with no significant cytotoxicity in HEK 293 and L929 cell lines. Thus, our studies show that holanamine can further be used to develop effective antileishmanial agents against evolving drug-resistant parasites.

The ChaC family of γ-glutamyl cyclotransferases is required for Leishmania to switch to a slow growth state and for long-term survival of the parasite

The ChaC family of γ-glutamyl cyclotransferases is conserved throughout all Kingdoms and catalyzes the degradation of GSH. So far, the ChaC family proteins in trypanosomal parasites are missing in the literature. Here, we report two members of the ChaC family of γ-glutamyl cyclotransferases (LmChaC_2a and LmChaC_2b) in the unicellular pathogen Leishmania. Activity measurements suggest that these proteins catalyze degradation of GSH but no other γ-glutamyl peptides. Recombinant LmChaC_2a protein shows ∼17-fold lower catalytic efficiency (k_cat ∼ 0.9 s⁻¹) than LmChaC_2b (k_cat ∼ 15 s⁻¹), although they showed comparable K_m values (∼1.75 mM for LmChaC_2a and ∼2.0 mM for LmChaC_2b) toward GSH. qRT-PCR and Western blot analyses suggest that the LmChaC_2a protein was found to be constitutively expressed, whereas LmChaC_2b was regulated by sulfur stress. To investigate its precise physiological function in Leishmania, we generated overexpressed, knockout, and complement cell lines. Flow cytometric analyses show the presence of a higher intracellular GSH concentration and lower intracellular ROS level, indicative of a more reductive environment in null mutants. We found LmChaC2-expressing cells grow in GSH-containing sulfur-limited media, while the null mutants failed to grow, suggesting that LmChaC2 is crucial for cell growth with GSH as the only sulfur source. Null mutants, although reach the stationary phase rapidly, display impaired long-term survival, indicating that LmChaC2-mediated GSH degradation is necessary for prolonged survival. In vivo studies suggest that LmChaC2-dependent controlled GSH degradation promotes chronic infection by the parasite. Altogether, these data indicate that LmChaC2 plays an important role in GSH homeostasis in Leishmania.

The state of the art of extracellular vesicle research in protozoan infection

Protozoan diseases seriously affect the health of human beings, livestock and poultry and lead to high economic and medical costs. Extracellular vesicles (EVs) are membranous structures formed through biological processes that play important roles in immune regulation. Studies have shown that parasites transmit information to hosts through EVs to modulate host immune responses. The major roles played by EVs released from parasites involve facilitating parasitization of the host. In this review, we discuss relevant recently obtained data on EVs secreted by different kinds of protozoa, including their molecular mechanisms, and discuss the roles played by EVs in the occurrence and development of parasitic diseases.

Molecular characterization of glyceraldehyde-3-phosphate dehydrogenase from Eimeria tenella

Chicken coccidiosis is an extremely common and lethally epidemic disease caused by Eimeria spp. The control measures of coccidiosis depend mainly on drugs. However, the ensuing drug resistance problem has brought considerable economic loss to the poultry industry. In our previous study, comparative transcriptome analyses of a drug-sensitive (DS) strain and two drug-resistant strains (diclazuril-resistant (DZR) and maduramicin-resistant (MRR) strains) of Eimeria tenella were carried out by transcriptome sequencing. The expression of glyceraldehyde-3-phosphate dehydrogenase of E. tenella (EtGAPDH) was upregulated in the two resistant strains. In this study, we cloned and characterized EtGAPDH. Indirect immunofluorescence localization was used to observe the distribution of EtGAPDH in E. tenella. The results showed that the protein was distributed mainly on the surface of sporozoites and merozoites, and in the cytoplasm of merozoites. qPCR was performed to detect the transcription level of EtGAPDH in the different developmental stages of the E. tenella DS strain. The transcription level of EtGAPDH was significantly higher in second-generation merozoites than in the other three stages. The transcription level of EtGAPDH in the different drug-resistant strains and DS strain of E. tenella was also analyzed by qPCR. The results showed that the transcription level was significantly higher in the two drug-resistant strains (MRR and DZR) than in the DS strain. As the concentration of diclazuril and maduramicin increased, the transcription levels also increased. Western blot results showed that EtGAPDH protein was upregulated in the DZR and MRR strains. Enzyme activity showed that the enzyme activity of EtGAPDH was higher in the two resistant strains than in the DS strain. These results showed that EtGAPDH possess several roles that separate and distinct from its glycolytic function and maybe involved in the development of E. tenella resistance to anticoccidial drugs.